This section provides background information related to the present disclosure which is not necessarily prior art.
In aluminum cylinder blocks for engines of automobiles (hereinafter referred to as cylinder block), cylinder liners (hereinafter sometimes referred to as liner) made of cast iron are often used in order to satisfy desired seizing resistance and wear resistance of a sliding surface. As a method for producing the cylinder block having the liner enveloped or embedded therein, a method for enveloped casting has been known wherein a liner is placed within a cast mold for the cylinder block and the periphery of the liner is enveloped with aluminum or an aluminum alloy (hereinafter referred to as an aluminum material).
In such a liner, it is required to secure adhesion between the outer face of the liner and the aluminum material to prevent the liner from rotating at the time of processing the inner face of the liner after the enveloped casting or to improve the engine performance by the reduction in the deformation of bores and the improvement of thermal conductivity. The following methods have been known to obtain a liner having a high adhesion with the aluminum material:                (1) a method wherein shot peening is applied to the outer face of the liner to provide irregularities on the outer face, thereby improving the adhesion (JP-B-2-29426);        (2) a method wherein spinies (acicular special cast surface) are formed on the outer face of the liner to improve the adhesion (JP-B-43-4842);        (3) a method wherein grooves in an axial direction are formed by machining the outer face of the liner to improve the casting properties of the block and the adhesion (JP-A-8-290255); and        (4) a method wherein blast finishing is applied to the cast iron surface of the outer face of the liner. It has been known that the cast iron surface in this case is obtainable by a permanent mold centrifugal casting method or the like wherein a suspension containing from 20 to 40 mass % of diatomaceous earth having a mean particle size of not more than 0.1 mm, from 2 to 10 mass % of bentonite and from 65 to 80 mass % of water, is coated by spraying on the cast mold, and after drying it, a melt of cast iron is poured thereinto.        
However, the above methods (1) to (4) have the following drawbacks. For example, with the shot peening in the above method (1), the adhesion is insufficient, and further, since a soft ferrite structure is required to exist in a thickness of at least 2.0 mm, the thickness tends to increase. In the above method (2), although the adhesion is good, the irregularities on the outer face is at a level of about 1.0 mm and the thickness increases, and further, the filling property of the aluminum material into the dents of spinies is poor. In the machining of grooves in the above method (3), the thickness tends to increase entirely in order to secure the strength at the bottom of groove, and the cost tends to be high. The above method (4) obtainable by blasting the cast iron surface has drawbacks, e.g. poor adhesion, although the filling property of the aluminum material is good and the price is low.
It would be desirable to develop a cylinder liner having a high clamping performance between the cylinder liner and an associated engine block.